ACTIONSCRIPT 3 Developer’s Guide en

ACTIONSCRIPT 3.0 DEVELOPER’S GUIDE
Working with Pixel Bender shaders
Each ShaderParameter object also has an index property that indicates where the parameter fits in the order of the
shader’s parameters. In addition to these properties, a ShaderParameter object can have additional properties
containing metadata values provided by the shader’s author. For example, the author can specify metadata values such
as minimum, maximum, and default values for a parameter. Any metadata values that the author specifies are added
to the ShaderParameter object as dynamic properties. To examine those properties, use a for..in loop to loop over
the ShaderParameter object’s dynamic properties to identify its metadata. The following example shows how to use a
for..in loop to identify a ShaderParameter object’s metadata. Each metadata value is added to a Vector instance
named metadata. Note that this example assumes a Shader instance named myShader is already created, and that it is
known to have a parameter named brightness:
var brightness:ShaderParameter = myShader.data.brightness;
var metadata:Vector. = new Vector.();
for (var prop:String in brightness)
{
if (brightness[prop] is String)
{
metadata[metadata.length] = brightness[prop];
}
}
// do something with the metadata
Using a shader
Flash Player 10 and later, Adobe AIR 1.5 and later
Once a Pixel Bender shader is available in ActionScript as a Shader object, it can be used in several ways:
Shader drawing fill: The shader defines the fill portion of a shape drawn using the drawing api
Blend mode: The shader defines the blend between two overlapping display objects
Filter: The shader defines a filter that modifies the appearance of visual content
Stand-alone shader processing: The shader processing runs without specifying the intended use of the output. The
shader can optionally run in the background, with the result is available when the processing completes. This
technique can be used to generate bitmap data and also to process non-visual data.
Using a shader as a drawing fill
Flash Player 10 and later, Adobe AIR 1.5 and later
When you use a shader to create a drawing fill, you use the drawing api methods to create a vector shape. The shader’s
output is used to fill in the shape, in the same way that any bitmap image can be used as a bitmap fill with the drawing
api. To create a shader fill, at the point in your code at which you want to start drawing the shape, call the Graphics
object’s beginShaderFill() method. Pass the Shader object as the first argument to the beginShaderFill()
method, as shown in this listing:
var canvas:Sprite = new Sprite();
canvas.graphics.beginShaderFill(myShader);
canvas.graphics.drawRect(10, 10, 150, 150);
canvas.graphics.endFill();
// add canvas to the display list to see the result
Last updated 6/6/2012
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